This invention relates to a method and apparatus for continuously monitoring the respiration of patients, particularly critically ill patients in intensive care units.
Most methods used in the past involve the use of face masks or mouthpieces, which is not only invasive and discomforting to the patient, but also disturbs the very breathing patterns being measured. These prior art methods may require cooperation from the patient, impossible if the patient is critically ill or perhaps comatose, and mouthpieces certainly may not be left in place for continuous monitoring. Other prior art methods which are less disturbing for the patient and his breathing pattern, such as use of a pneumograph, are incapable of providing data of sufficient accuracy for clinical use.
One prior art approach measured changes in the thickness of the chest by placing coils on the front and back, sending an alternating current through one coil, and detecting the voltage induced in the other coil. The equipment used was somewhat bulky, and the linear changes in chest thickness did not represent breathing volumes very well. It did have the advantage of not requiring face masks or mouthpieces, however.